noise feedback coding （NFC） has attracted renewed interest with the recent standardization of backward-compatible enhancements for ITU-T G.711 and G.722. It has also been revisited with the emergence of proprietary ...
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noise feedback coding （NFC） has attracted renewed interest with the recent standardization of backward-compatible enhancements for ITU-T G.711 and G.722. It has also been revisited with the emergence of proprietary speech codecs, such as BV16, BV32, and SILK, that have structures different from CELP coding. In this article, we review NFC and describe a novel coding technique that optimally shapes codingnoise in embedded pulse-code modulation （PCM） and embedded adaptive differential PCM （ADPCM）. We describe how this new technique was incorporated into the recent ITU-T G.711.1, G.711 App. III, and G.722 Annex B （G.722B） speech-coding standards.
In an all-digital, class-D audio amplifier, pulse-width-modulation (PWM) of a digital signal source is usually followed by a low-order analog low-pass filter to construct the analog audio waveform. This study shows ho...
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In an all-digital, class-D audio amplifier, pulse-width-modulation (PWM) of a digital signal source is usually followed by a low-order analog low-pass filter to construct the analog audio waveform. This study shows how to remove the non-linear distortion usually associated with PWM, by prefiltering the digital signal prior to the PWM mapping in such a manner that the overall result is distortion-free. The prefiltering is done using computationally effective infinite-impulse-response filters combined with short-kernel anticausal finite-impulse-response filters, and relies on the interpretation of PWM as a Volterra filter. A case study is presented where a second-order Butterworth analog low-pass filter is used for reconstruction of the analog audio signal. A complete amplifier system is modelled, including upsampling, Volterra prefiltering and noise feedback coding. Computer simulations on CD music signals were performed. Using a third-order prefilter, a signal-to-noise ratio of 97-102 dB was obtained for the music signals tested. All necessary filter data needed for realisation of the prefilter are given in the Appendix.
This paper describes the BroadVoice (R) speech coding algorithm, which has been standardized as PacketCable (TM), SCTE (R), and ANSI standards for VoIP cable telephony. The BroadVoice family of codecs includes a 16 kb...
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ISBN:
(纸本)1424407281
This paper describes the BroadVoice (R) speech coding algorithm, which has been standardized as PacketCable (TM), SCTE (R), and ANSI standards for VoIP cable telephony. The BroadVoice family of codecs includes a 16 kb/s BroadVoice16 narrowband codec and a 32 kb/s BroadVoice32 wideband codec. BroadVoice is based on two-stage noise feedback coding with vector quantization of excitation and is optimized for low delay, low complexity, and high quality. It has an algorithmic delay of merely 5 ms and a complexity of only 12 and 17 MIPS for BroadVoice16 and BroadVoice32, respectively. The speech quality of BroadVoice16 is better than that of G.728, G.729, and 32 kb/s G.726. The speech quality of BroadVoice32 is better than that of 64 kb/s G.722.
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